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5.
OPTIMIZING INSTRUMENT STABILITY AND SAMPLE
MOUNTING
Optimizing the experiment conditions and sample mounting can greatly improve the quality of the
indentation. During an indentation, environmental stability, sample stability and probe suitability define
the quality of the experimental dataset. In case the indentation results show irregularities or high noise,
it is worth considering the factors as described below.
5.1
Environment stability
The Pavone is engineered to operate as independently from the environment as possible. Nonetheless, it
is still possible for the environmental conditions to influence and compromise measurement results.
Temperature
In order to minimize the measurement error due to temperature drift, sudden room or medium
temperature changes should be avoided when measuring. Verify that the Pavone is mounted away from
any air-conditioning, heating, or ventilation vent. The built-in temperature control system can be used to
measure samples at physiological temperatures. Be aware that the temperature system can also
introduce drift in the measurement if the sample or medium temperature has not yet reached an
equilibrium state.
As a result, you will see that the signal is not on the demodulation circle and requires
recalibration.
Vibrations
To minimize the measurement error due to mechanical disturbances, such as ground vibrations from
other labs, other equipment, or appliances, ensure that the Pavone is mounted on a stable bench.
Preferably this bench is not shared with other vibrating machines such as vortexes, pumps, or large fans.
Optionally the Pavone can be bolted to the top of a third-party stabilization platform, such as an air table.
Make sure that the air table is inflated when using Pavone.
Mechanical instability can also originate from the sample container or sample substrate contact with the
Pavone
sample stage. In order to get the best measurement possible, the complete ‘measurement loop’,
i.e. everything between the probe and the sample stage base plate, should be free from instability and
be as stiff as possible. This can be achieved by ensuring good and stable contact between the sample
carrier/wellplate and the Pavone sample stage, and by using stiff substrates and containers. Less stiff
sample carriers, such as trans-well membranes, may be used, but it is advised to check the stability of the
sample carrier or the insert when mounting it into the Pavone.
5.2
Probe stability
Solution temperature
When immersing the probe in a liquid of a different temperature, such as refrigerated liquids or liquids
obtained from the incubator, wait upon immersion before starting calibration. The probe and medium
must reach equilibrium in temperature. This can be observed by the interferometer signal: if the voltage
is changing when the probe is immersed, i.e. the signal is drifting, it means that the probe and medium
